Question about the git version during build

Hello

I have a question about the git version number. In December i have downloaded a copy of Kodi from git. I have put all files into c:\kodi and prepared the build by executing the scripts. I was able to compile Kodi and i have received
the setup with the name KodiSetup-20161219-712d562-Krypton.exe. After starting Kodi i have the version Kodi 17.0 RC2 Git 20161219-712d562-dirty compiled 2016.12.19

Today i did the same and i have downloaded a copy from git and put the files into c:\kodi again. I have overwritten all files. I have started the build again and i was able to build a new setup.
The name of the Kodi setup is KodiSetup-20161219-712d562-Krypton.exe again but if i start Kodi i have Kodi 17.0 RC3 Git 20161219-712d562-dirty compiled 2017.01.13

Can someone explain why the git number is the same? I noticed in the official build the number is 20170111-4d93228-d

What do i miss? What do i have to do that the git number is the correct one?